Method of making patterned metal coatings by selective etching of metal

ABSTRACT

Web substrates (such as plastic film) are coated with metal (as by vacuum aluminizing) and etched in selected areas of the metal coating. The etching medium comprises an etchant, a body-forming member to trap the etchant, a volatile carrier and a dispersing member which holds the etchant and body-forming member in intimate mixture.

UnIted States Patent 3,647,508

Gorrell 1 Mar. 7, 1972 [54] METHOD OF MAKING PATTERNED 3,234,137 2/1966Lemaire et al ..252/79.4 METAL COATINGS BY SELECTIVE 3,346,384 10/1967Gaynor I I ..96/36 I G 0 ET 3,482,976 12/ 1969 Schaefer et al. ..96/363,489,563 1/1970 Schaefer ..96/36 1 lnvenw" John 60m, Bllleflcar Mass-3,516,346 6/1970 Schaefer ..96/36 [73] Assgnee Them FOREIGN PATENTS ORAPPLICATIONS [22] Filed: Aug. 27 1968 647,573 12/1950 Great Britain..117/11 1 1 pp ,627 Primary ExaminerRalph S. Kendall Attorney-Harness,Dickey & Pierce [52] U.S.Cl ..117/38, 117/8, 156/7,

, 156/4, 252/79.4, 252/795 [571 ABSTRACT [5 1] 'f Cl 1/22 Web substrates(such as plastic film) are coated with metal (as [58] Fleld 01 Search117/38, 8, y vacuum aluminizing) and etched in l d areas f h 156/l 10252/79/7794 96/36 metal coating. The etching medium comprises anetchant, a [56] References Cited body-formmg member to trap the etchant,a volatIle carrIer UNITED STATES PATENTS Graham et al. ..156/7 X and adispersing member which holds the etchant and bodyforming member inintimate mixture.

8 Claims, 3 Drawing Figures PAIENIEQMAR 7 I9?2 3, 647, 508

C FIG.3

METHOD OF MAKING PA'I'IERNED METAL COATINGS BY SELECTIVE ETCI-IING FMETAL The present invention relates to the art of metal coating andparticularly to metal coatings deposited on flat web substrates.Examples of common products in this field are plastic film or textilescoated with aluminum by vacuum deposition, steel strip coated with tinby dipping, paper coated with aluminum foil by lamination. The metalcoating may be for decorative purposes and/or functional purposes, basedon the essential characteristics of adhesion, reflectivity andconductivity of the metal coating. Some of the uses for such metallizedwebs are packaging, hot stamp printing, draperies, clothing andblankets, capacitors, resistors, electrical circuitry, microwave andlight reflectors and thermal insulation.

BACKGROUND It is a longfelt need in the art of metallizing and severalof the various fields of application of metallized webs to establishpatterns in the metal coating. This can be done by electrically sparkingaway portions of the metal coating as in US Pat. No. l,909,079, etchinglongitudinal stripes in the coating by contacting with an etch coatedwheel as taught in US. Pat. No. 2,897,066, use of masking or stencils inthe original application of the coating, multiple coating steps withdifferent masks, and photoresist masking followed by etching. It is alsoknown to pattern metal surfaces by anodizing and selectively etching theoxide as shown for instance in US. Pat. Nos. 3,016,293 and 3,017,285. Itwas also suggested in the abovecited US. Pat. No. 2,897,066 that anetchant used for demetallizing longitudinal stripes of aluminum might,if its viscosity were adjusted to that of printers ink, be applied byprinting rolls or galleys. The likelihood of success of the lattersuggested method is limited by the conflicting requirements of viscosityadjustment to prevent the etch from spreading and complete etching ofthe desired pattern area and is not known to have been successfullyapplied, even for the limited striping function contemplated by thepatentee. The coating while masking, sparking and etch methods are allessentially limited to producing straight lines in the longitudinaldirection of the web. The photoresist and etch method can producebidirectional patterns of coating metal removal, but is expensive.

OBJECTS It is an object of the present invention to provide an improvedmethod of making metal coated webs with patterns in the coatings whichis more practically feasible and economical than prior art methods. Ingeneral the object is achieved by printing an etch medium on the web,the medium containing an etchant and other components as hereindescribed.

It is a further object of this invention to achieve a high degree ofcontrol of the pattern formed so that formation can be limited toselected areas of the coating. It is a related further object of theinvention to form bidirectional patterns that is, patterns which extendtransversely to the web as well as longitudinally, in contrast tocapacitor electrode patterns which are simple longitudinal stripes ofmetal removal running along the length of a metal coated plastic film.Examples of bidirectional patterns are repetitive transverse stripes,circles, stars, number or letter patterns of metal removal containedsingly or in a repetitive pattern along the length of a metal-coatedplastic film.

It is a further object of the invention to provide for altemative massproduction utilization or custom use of the metal removal technique andto similarly provide alternative products of metal coated webs withpreformed patterns of metal removed or metal coated web which are inprecursor form and capable of patterned metal removal by a simple finalstep.

GENERAL DESCRIPTION The invention comprises an improved method ofpreparing patterned webs by metal coating and patterned metal removal byetching, including species of applying etching medium before or aftermetal coating, an improved method of patterning metal-coated webs, theproducts of the foregoing methods and new etching media and theirpreparation for use in the abovestated methods.

The etching medium comprises a mixture of an etchant, a body-formingmember and a volatile carrier. It may also comprise a separatedispersing member, if necessary to hold the etchant and body-formingmember. in intimate mixture. The medium is applied to the coating in thedesired pattern by print techniques and heated for drying.Alternatively, the medium may be applied in a latent form and activatedin precise pattern areas only. In either case, etching proceeds in thepattern area simultaneously with solidification of the body-formingmember to form a spongelike trap for the etchant limiting its spread tothe pattern area.

The resultant chemical complex is easily removed to expose the websubstrate in the pattern area. Whether the etch residue is retained orwashed away, the etched pattern area differs in essentialcharacteristics of conductivity adhesion and/or reflectivity from theremainder of the metal coating. The patterned web can then be cut todesired size for use as packaging, draperies, printed circuits, etc.

The present invention is particularly flexible in its various methods ofusage. The principal metal coating, print-etching and size-coating steps(with appropriate adjustments described below) (1) can be any sequentialorder, (2) can be done separately or in close-together sequence, (3) canutilize conventional materials or methods and apparatus such ascommercially available metallized webs, commercially available printingfacilities and web handling, cutting and heating facilities, andconventional cheap chemicals and (4) allows economic material usage inthat major components, such as metallized web can be mass produced anddoled out in portions for custom print-etching of desired patterns.

Other objects, features and advantages of the present invention will inpart be obvious and will in part be stated herein.

SPECIFIC DESCRIPTION AND DRAWINGS The invention is now specificallydescribed with reference to the accompanying drawings wherein:

FIG. 1 is a diagram of an apparatus for carrying out the method of theinvention,

FIG. 2 is a segment of finished product produced by the inventionaccording to a preferred embodiment,

FIG. 3 is a cross section view showing a product according to anotherembodiment of the invention and indicating its mode of utilization.

This specific description is made with respect to the illustrativeapplication of the invention to aluminum-coated web stock.

The invention can be practiced with the use of a felt-tipped pencil orink stamp for applying etch to the aluminum coating. However, it ispreferred and distinctly advantageous to utilize the invention inconnection with mass production of patterned metal coated web stock.

In this preferred embodiment, the method steps are:

I. Vacuum aluminize a substrate roll through evaporation of aluminum ina vacuum chamber and condensation on a substrate web which is unrolledfrom a roll supply in the vacuum chamber, passed over the evaporatingaluminum and then rerolled.

II. Removal of the coated web roll from the vacuum chamber andprint-etching in the apparatus of FIG. 1.

The FIG. 1 print-etching apparatus is essentially a conventionalprinting apparatus modified for use in the present invention. A rolledup web of metallized plastic is unrolled from a supply roll 102 and fedto a takeup roll 104. The print etch mixture bath 2 is picked up by anetched gravure roll 4 containing a screen pattern etched on its face.The pickup roll 4 rotates past a doctor blade 5 and into contact with aprint roll (gravure or mountable type) which has a printed faceenforclmma ing to the desired pattern, the etch area being raised and itpicks up the print etch mixture in the desired pattern and transfers itto the web via transfer roll 8. The transfer roll 8 is optional. Thescreen count of roll I4 is preferably 50 to 100 mesh per inch for mostetch mixtures. But this is variable over a wider range.

The web passes over press roll 10 while receiving the pattern ofprint-etch mixture and then goes past an infrared heater 12 where theapplied print etch mixture is dried to set up the pattern of metalremoval. The web is then passed over guiding rolls 14, 16, 22, 28, 30 toroll 104. On the way it passes through a water bath 18 and spray waterrinses 20, infrared heater 24 and blowing air jets 26 to dry the water.

A typical resultant product is shown in FIG. 2 which illustrates asection of plastic film web (1,000 feet long or longer) P with a metalcoating M. The length direction of the web is indicated by L and thetransverse dimension by T.

Running along the length of the web are two repetitive etch patterns Bwhich are bidirectional, that is extending transversely as well asmerely longitudinally. In a sense, the interruptions between likepatterns along the length are also part of the bidirectional characterof the pattern. The two repetitive patterns shown for illustration areof triangle and L-form. But far more complex patterns have been etched,including the letters of the alphabet in normal type face with a centralisland of metal remaining intact in the etched letter 0. It should beappreciated that the etchant could be applied over very large areas ofthe metal coating to leave discrete islands of metal rather than etchingsmall areas out of the metal coating, as in the preferred embodimentillustrated in FIGS. 1-2.

The print-etch mixture as described above in the general description hasan etchant component, a body-forming member, a volatile carrier and,preferably a dispersing agent for extending stability, or shelf life, ofthe mixture. Also, the mixture may optionally include viscosityadjusting components; however, viscosity control is less important thanetchant and mixture stability. In the FIG. 1-2 embodiment, the mixtureis preferably wet when applied. Alternatively, it may be applied dry andwetted in situ to begin etching. The next and critical step (III) in theetching is drying the mixture by driving off the volatile carrier toallow the bo;y-forrning member to harden. The drying may be done byletting stand in room temperature air. But preferably it is done byassisted heating. The cured body forming member forms a spongelikestructure which limits the etchant to the pattern area where it attacksthe aluminum metal coating to form a complex of aluminum and the mixturein the pattern area lacking the essential characteristics of adhesionreflectivity and conductivity of the original metal coating.

In the next (and optional) step IV, the chemical complex is removed byrinsing with water or solvents and/or brushing to leave the pattern areabare.

For aluminum, the etchant is preferably sodium hydroxide or potassiumhydroxide. In order to increase the intensity of etching for attackingthick aluminum coatings at high rates for mass production, the etchantis preferably highly concentrated.

The body-forming member is selected from any of several classes ofnatural or synthetic resins including vinyl, acetal, acrylic andpolyurethane resins. Several of these are known for usage in printersinks or paint thickeners. Stability is a principal criterion.

The volatile carrier is a common economic organic solvent such as methylethyl ketone. I

The dispersing agents include methyl alcohol and other ethereal solventextenders, sodium carboxy methyl cellulose and silicones.

The carrier and dispersing agent may be initially associated with thebody-forming member, the etchant or both.

The same material may be the carrier in one combination and a dispersingagent in another combination. For instance,

in one combination methyl ethyl ketone would be a dispersing agent, ordiluent for a boy of acetal resin dissolved in a toluol carrier andmixed with an aqueous etchant. In many other combinations, methyl ethylketone is the carrier.

A particularly critical problem is the avoidance of shocking out of themixture through formation of precipitates or layers of liquid (thecommon antipathy of oil and water oil from the carrier, water from theetchant).

The balancing of the various criteria of etchant concentration, solutionstability and high speed etching will best be understood by reviewingthe following nonlimiting illustrative examples which show instances ofsuccessful, and unsuccessful, print-etching achieved through variousmixture formulations and mixing procedures.

EXAMPLE 1 A sheet of green open weave polyester fiber cloth (Dacron T.M.of E. I. DuPont de Nemours) was vacuum metallized to produce adecorative grade coating with a bright metallic appearance which wascomplete across the face of the sheet. The sheet was hand stamped withan ink stamp containing a variety of printed matter which was inked byrolling on the stamp an etchant mixture liquid prepared as follows:

1. Mix 10 parts of 55 percent acrylic solution (Union Carbide 00200)with 20 parts of ethylene glycol monoethyl ether (Cellosolve solvent)and 20 parts of water;

2. Mix (1) with 60 parts of 50 percent sodium hydroxide solution;

3. Mix 60 parts methyl ethyl ketone with 30 parts water;

4. Mix (2) with (3).

All mixing steps are carried out with stirring and without heataddition. The resultant liquid was very fluid and spread easily on thestamp.

After the stamp was inked and applied to the cloth, the cloth was heldup to a radiantheater with a fan for a few seconds. After the heatingthe etch took place rapidly in the stamped area of the cloth a fewseconds formed a powdery residue which was then rinsed away with water.

The resultant stamped pattern on the cloth was very sharp andessentially complete within the pattern area. The original green clothsurface in the stamp area made a sharp contrast with the metallicbrightness in the surrounding. For comparison, the same stamp was inkedon a conventional stamp inking pad and applied to a piece of whitepaper. The resultant A pattern was no more defined and was less completewithin the. pattern areas than the B pattern formed on metallized clothby etching.

EXAMPLE 2 The mixture of Example 1 was applied to a nylon cloth with thesame good results.

EXAMPLE 3 A half-mil film of polyethylene terephthalate polyester(Mylar-T.M. of E. I. DuPont de Nemours) was vacuum aluminized to adecorative grade thickness of 5 ohms per square.

The metallized film was hand-stamped by a stamp prewet with an etchingmixture prepared as follows:

1. Mix 50 parts of 55 percent acrylic solution with parts methyl ethylketone. 2. Mix 50 parts methyl alcohol with 10 parts Cellosolv and 50parts of 50 percent sodium hydroxide. 3. Mix l and (2). The metallizedfilm was stamped and heated to dry the etching mixture as in Example 1Good etching was obtained.

EXAMPLE 4 220 parts of the mixture of Example 3 were added to 55 partsof additional 55 percent acrylic solution and used for etching as inExample 3 with good results.

EXAMPLE 5 200 parts of the mixture of Example 3 were added to 50 partsof a polyvinyl butryal (PVB) solution (5 percent in a mixed solvent of1:1 ratio isopropyl alcohol and Cellosolv) and used for etching as inExample 3 with good results.

EXAMPLE 6 The following formulation failed to etch when used for etchingas in Example 3.

1. Mix 50 parts of the acrylic solution with 50 parts of the PVBsolution and 50 parts of methyl ethyl ketone.

2. Mix 50 parts of the sodium hydroxide (50 percent) solution with 40parts methyl alcohol and parts Cellosolv.

3. Mix (1) and (2). It was observed that after mixing step (3) aprecipitate formed within the mixture.

EXAMPLE 7 200 parts of the mixture of Example 3 were added to 50 partsof sodium hydroxide solution and used for etching as in Example 3 withgood results. The mixture formed a gel instead of the usual fluidliquid, but was nevertheless readily picked up and applied by the handstamp.

EXAMPLE 8 Aluminum coatings were vacuum deposited on vinylidenechloridecoated cellophane and polyester film substrates and etched as in Example3 with a mixture formulation prepared as follows:

1. Mix 50 parts acrylic with 100 parts methyl ethyl ketone and 50 partsmethyl alcohol. I

2. Mix 10 parts Cellosolv and 50 parts of the sodium hydroxide solution.

3. Mix (1) and (2). The etching results were good, but the etchingprocess tool a few seconds longer after drying than the previoussuccessful examples.

EXAMPLE 9 240 parts of the Example 8 mixture were added to 30 parts ofsodium hydroxide solution. The resultant mixture gave good etching atthe usual high speed.

EXAMPLE 10 A mixture formulation was prepared as follows and had aviscosity of about 30 seconds on a No. 3 Zahn cup. It was used foretching and gave good results.

1. Mix 50 parts of the PVB solution with 10 parts Cellosolv and 50 partsmethyl ethyl ketone.

2. Mix 50 parts sodium hydroxide solution (50 percent) with 50 partsmethyl alcohol.

3. Mix l) and (2), adding (2) to l while stirring.

EXAMPLE 1 l 100 parts of the Example 10 mixture were mixed with partswater and 25 parts acrylic solution. The resultant mixture gave goodetching effect.

EXAMPLE l2 Metallized plastic and cloth sheets were patterned etch withgood results using the following mixture formulation:

1. Mix50 parts water with 5 parts of 5 percent solution of sodiumcarboxymethyl cellulose in water.

2. Mix 50 parts methyl alcohol with 50 parts methyl ethyl ketone and 50parts of 55% acrylic solution.

3. Mix (1) and (2).

4. Mix (3) with 50 parts of 50 percent sodium hydroxide solution.

EXAMPLE 13 Aluminum coated Mylar was etched well, but at a slower rate,with the following formulation:

1. Mix 100 parts 55 percent acrylic solution with 50 parts methyl ethylketone and 50 parts isopropyl alcohol. 2. Mix 20 parts Cellosolv and 50parts of 50 percent sodium hydroxide solution.

Anll

EXAMPLE 14 Fast and good etching of aluminized Mylar was achieved usinga formulation of 20 parts of 50 percent sodium hydroxide solution mixedwith 200 parts of the Example 13 mixture.

EXAMPLE i 5 The following formulation was attempted.

1. Mix parts of the Example 14 mixture with 10 parts of Cellosolv.

2. Mix 20 parts of 50 percent sodium hydroxide with l 3. Mix 40 partsmethyl ethyl ketone with (2). The mixture shocked out separating intolayers on standing.

EXAMPLE 16 The Example 15 mixture was restirred and 20 parts of it weremixed with 30 parts of water and 20 parts of 50 percent sodiumhydroxide. The resulting mixture shocked out.

EXAMPLE 17 Etching was unsuccessful with the following formulation:

1. Mix 20 parts glyoxal with 10 parts methyl ethyl ketone.

2. Mix l with 20 parts 55 percent acrylic solution.

3. Mix (2) with 10 parts 50 percent sodium hydroxide solution.

EXAMPLE 1 8 EXAMPLE l9 10 parts of 50 percent sodium hydroxide solutionwere mixed with 15 parts Cellosolv and the Example 18 mixture. Theresultant was very cloudy but nevertheless successfully used in etchingaluminized Mylar.

EXAMPLE 20' A series of etching mixtures were made with solid alkalimetal hydroxide to increase intensity of etching action. These were a.grams of potassium hydroxide dissolved overnight in a solvent mixture of100 ml. methyl ethyl ketone and 100 ml. Cellosolv to produce a darkbrown thick mixture.

. 2 grams of sodium hydroxide partially dissolved overnight in 20 ml.Cellosolv to produce a yellow solution and mixed with a mixture of 20ml. 55 percent acrylic solution in 20 m1. methyl ethyl ketone andfinally mixed with 15 ml. Dow Corning DC 600 silicone to produce a lightbrown mixture.

c. 10 ml. of 55 percent acrylic solution with 20 ml. of (a) above.

d. 15 ml. of (a) above in 15 ml. of methyl alcohol and mixed with 10 ml.55 percent acrylic.

All the foregoing mixtures were picked up on the tip of a glass rod andapplied to aluminized Mylar and successfully etched small spots in thealuminum coating. All the etches were repeated by using the rod to add adrop of water to the contact zone which speeded etching. The mixtures of(c) and (d) were completely homogeneous and (a) and (b) had some initialundissolved caustic. However, all four mixtures demonstrated good shelflife of several days before shocking out via layering or precipitatecompared to 1-2 days for most of the previous examples. An odor ofevolving ammonia was noted over mixtures (b), (c) and (d) whichcontained acrylic resin.

EXAMPLE 21 10 parts of the Example (a) mixture were mixed with 10 partsof a 30 percent solution of Lewisol-28 solid (a maleic resinmodified'resin ester solid) dissolved overnight in methyl ethyl ketoneand formed a completely homogeneous solution with shelf life of severaldays. Since it was completely free of acrylic-amide body member it didnot evolve ammonia.

The mixture did not, per se, etch metal noticeably when applied with arod and to aluminized Mylar, but did etch when as little as a tracedroplet or as much as 1 ml. of water was added to the contact area.

EXAMPLE 22 18 ml. of the Example 21 mixture (including 1 part water in18) and 12 ml. of the Example 20 (a) mixture were mixed and applied toan artist's hand roller and used for etching aluminized Mylar with goodresults over the very large area of roller contact with the metal coat.

EXAMPLE 23 To further increase shelf life consistent with high intensityetching, a new series of mixtures was made as follows:

a. 20 ml. of the Example 21 mixture (including 1 part water in 20) mixedwith 0.1 ml. DC-600 silicone. b. -20 ml. of etch solution (of 100 gramsNaOH dissolved in a 100 ml. Cellosolv 100 ml. methyl ethyl ketonesolvent) were mixed with 30 ml. of methyl ethyl ketone and 30 ml. of theabove described solution of Lewisol-28. c. 20 ml. of the etch solutionof (b) with 50 ml. of the (b) mixture and 0.5 ml. water. All threemixtures gave good roll-etching results and exhibited shelf livesof'several weeks. The etching was carried out on a very thick aluminumcoating (half-ohm per square).

EXAMPLE 24 100 ml. of methyl ethyl ketone was mixed with 100 ml.Cellosolv and 20 ml. water and heated to boiling 100 grams of KOl-lsolid was added to the boiling mixture. Upon cooling, there was somesolution separation. 80 ml. of methyl ethyl ketone was added andsolution separation was arrested This component demonstrated good shelflife and etching.

EXAMPLE 25 An etchant substantially similar to that of Example 24 etchedwell after mixing with a body component of Turco Guard 100 polyurethaneresin solution in equal amounts with etching speed increased byadjusting the mixture to a 60 40 ratio of etchant (including dispersingagent and carrier) to resin solution.

The foregoing examples illustrate some of the variety of factorsinvolved in choosing the components of the etching medium or adjustingthe print-etch process steps to suit a particular print etchapplication. Some of the key criteria may be summarized as follows:

1. Where the print etching is to be accomplished by hand stamps orflexographic printing or the like, increased viscosity for handling onthe applicator is desired and this can be achieved by increasing thebody-forming member content and/or water content of the etching medium.On the other hand, viscosity normally has very little significant effecton the behavior of the etching medium on the metal since it is thesolidification of the body forming member, rather than wettability ofthe metal surface or viscosity of the medium which primarily controlspattern definition. For high speed printing, such as gravure or offset,lower viscosity (achieved by more solvent, less body and less dispersingagent or diluent or water) is preferred.

2. Another way of controlling viscosity is in the choice of bodymember-carrier subsystem. For instance a solution of Lewisol-28 inmethyl ethyl ketone has a lower viscosity than a solution of PVB in theisopropyl alcohol methyl ethyl ketone solvent, even though the twosolutions have the same solids content.

3. Where it is desired to fully remove the etch residue, choice of bodyforming member is important in regard to adhesion to the web substrate.Acrylic resins are easily washed off. In using some other body-formingmembers, it may be desirable to add soap or a wetting agent to theetching medium to expedite washing away.

Where it is desired to dispense with washing away residue and leave itin place, then the body choice factors are opposite.

Another degree of control over adhesion of the body is in the heatingfor drying. In all the foregoing examples, heating was carried out totemperatures allowing the bodyfforming resin to reach its green state(e.g., about l-200 F. for acrylic) but below the curing point (aboutC.). if it is desired to retain the etch residue to physicallyprotectthe substrate in the etch pattern area, this can be facilitatedby heating to curing. In this case, optical clarity can be enhanced byadding siloxanes to the etch medium.

4. For etching metal coatings of great thickness or at high productionrates, choices of more active etchants and higher concentration ofetchant are in order. The effective activity of the etchant can also beincreased by adding a salt to the etching medium which has oppositeelectrochemical characteristics compared to the etchant per se.

5. Shelf life or stability, is governed by choice of resin as noted inthe above examples. Reduction of water content and increase of solventand dispersant to increase stability is also significant factors.

6. The choice of thick depositing method for application of medium, suchas gravure printing, can compensate for the inherent dilution of etchantinvolved in (5) above.

OTHER COATINGS AND SUBSTRATES In applying the invention to othermaterials, the principal substitution in the above aluminum-attackingmixtures (media) would be that of the etchant. Acid-stable body-formingmembers, carriers and dispersing agents would be used. Suitable etchantsfor other metal coatings are well known. Some examples are for coppercoatings caustic or hydrochloric acid tin hydrochloric acid gold aquaregia nickel nitric or hydrochloric acid chromium hydrochloric or dilutesulfuric acid colbalt,

magnesium most acids iron ferric chloride or ferric sulfate solutions.

Metal alloys can be similarly etched by proper selection of etchant. Forinstance a film of nickel-chromium resistive alloy could be deposited onplastic and cuttings could be sold to electric circuit makers fordrawing out circuit patterns with a felt pencil impregnated with an etchme;ium.

The invention can be applied to multilayer metal coatings withpreferential attack of one layer. For instance, a copper coat could bedeposited over a silver coat and ferric chloride could be used to attackthe copper without substantial effect on the silver undercoat.Alternatively, a silver overcoat, over a copper undercoat, could beattacked by a nitric acid solution rich in copper ion, to pattern thesilver coat while leaving the copper coat intact. As another example, anickel iron magnetic alloy could be applied to a plastic film andovercoate; with aluminum to provide a magnetic shield. Windows could beprint-etched in the-aluminum shield using a medium containing causticetchant as described above.

Similarly metal web substrates can be coated with other metals (e.g.,aluminized steel, gold-steel clads) and the metal coating can bepreferentially etched without affecting the sub strate.

Other substrates such as packages, rods, spheres can be metal coated andthe coating can then be print-etched as described herein using rollers,stamps, pencils or automatic printing equipment.

OTHER BASIC EMBODIMENTS The foregoing discussion in this specificdescription of the invention has been essentially limited to thepreferred and distinctly advantageous approach of using the sequence ofsteps of (a) metal coating a substrate or obtaining a commerciallyavailable metal coated substrate, (b) print-etching a desired pattern inthe metal substrate, including the steps of applying the etching mediumto the coating in a defined pattern, drying the medium and optionallyremoving the etch residue, and (c) optionally cutting to a desired sizefor final use.

There are several general variations within the general scope of thepresent invention, many of which will be obvious and some of which arenow stated.

First, one may apply the print-etch pattern to the coated substrate in alatent form and activate it by heating and/or water addition at a muchlater time and/or after cutting to a desired final-use sizes. The latentetch may be applied broadly or in defined pattern areas, using a partialdrying and solidification of the body member to hold the pattern.Alternatively, the heating and/or water addition may be limited tospecific pattern areas. The water addition may be done by adding dropsof water or liberating water from a source in situ by heating. The insitu source may, for instance, be hydrated crystals contained in theetching medium, e.g., sodium silicate.

Second, the etching medium might be applied to the substrate directly ina latent form, and the metal deposited over the etching medium deposit.Such an embodiment would involve use of a precursor product which isillustrated in FIG. 3 a substrate, such as a plastic film web P, coatedwith an etching medium C and overcoated with a metal layer M. If themetal is applied by vacuum deposition, the substrate P with etch mediumsurface C should be cooled during the deposition. Etching in desiredpattern areas is initiated by holding a soldering iron I near thedesired pattern areas. As a specific variation of this embodiment, asuitable source of moisture for etching would be a choice of a highmoisture content substrate, e.g., cellulose acetate. As another specificvariation of this embodiment, the etching medium could be made to act asa release agent, either as applied or after degradation through time orchemical treatment. Thus, the metal film M could be stripped away aftercompletion of the etch-patteming operation. This would be an excellenteconomical source of ultrathin patterned metal for use in printedcircuit work.

In connection with the embodiment illustrated in FIG. 3 it should benoted that the etching medium could be selected to make amoisture-containing substrate suitable for vacuum deposition of metaland that the metal M protects the coating C from extraneous atmosphericmoisture during any storage period prior to etch activation.

Still further embodiments and variation in usage and practice of theinvention will be apparent to those skilled in the art once given thebenefit of the present disclosure. It is therefore intended that theforegoing specification and drawings shall not be construed as limitingexcept as set forth in the claims appended to this specification.

What is claimed is:

l. A continuous method of producing decorative or functionalbidirectional surface patterns on metal-coated substrate articlesutilizing adjacent areas of metallized and unmetallized surface on thesubstrate article by a printetch process comprising contacting themetallic coating with a substantially nonspreading etching mixture inregions of the coating constituting the desired bidirectional patternand drying the mixture to form a chemical complex of the metal and theetchant mixture which contains essentially all the metal in the patternregion and which lacks at least one of the essential characterlstics ofadhesion, reflectivity and conductivity of the metal coating per se,

wherein the substrate is of web form and, wherein the etching mixturecomprises two components in intimate contact and admixture, a first oneof said components comprising a body-forming solid dispersed in avolatile carrier the second component comprising the etchant so thatdrying of the mixture produces a solid which entraps the etchant in theregion of application of the mixture to limit spreading of the etchantduring the period while the etchant attacks the metal coating.

2. A continuous method of producing decorative or functionalbidirectional surface patterns on metal-coated substrate articlesutilizing adjacent areas of metallized and unmetallized surface on thesubstrate article by a print-etch process comprising contacting themetallic coating with a substantially nonspreading etching mixture inregions of the coating constituting the desired bidirectional patternand drying the mixture to form a chemical complex of the metal and theetchant mixture which contains essentially all the metal in the patternregion and which lacks at least one of the essential characteristics ofadhesion, reflectivity and conductivity of the metal coating per se,

wherein the substrate is of web form and, wherein the inhomogeneous wetetching mixture comprises a solution of resin in an organic carrier andan aqueous etching solution, the organic carrier having a highervolatility than water so that upon drying the mixture, solidification ofthe resin is quickly obtained to prevent spreading of the etchant.

3. A continuous method of producing decorative or functionalbidirectional surface patterns on metal coated substrate articlesutilizing adjacent areas of metallized and unmetallized surface on thesubstrate article by a print-etch process comprising contacting themetallic coating with a substantially nonspreading etching mixture inregions of the coating constituting the desired bidirectional patternand drying the mixture to form a chemical complex of the metal and theetchant mixture which contains essentially all the metal in the patternregion and which lacks at least one of the essential characteristics ofadhesion, reflectivity and conductivity of the metal coating per se,

wherein the etchant mixture comprises an etchant which is suitable forremoving the particular metallic coating, a body-forming component toprevent spreading of the etchant mixture when applied to the particularcoated substrate surface involved and a volatile carrier therefor and acomponent which prevents the etching and bodyfonning chemicals fromshocking out when contacted with each other, and heating the contactedarea to remove the volatile component of the etchant mixture to form acomplex of the metal coating contacted with the mixture and the etchantcomponent only in the selected portion of the coating contacted by themixture.

4. The method of claim 1 wherein the etching mixture is applied to themetal coating by precoating a solid applicator having a pattern faceconforming to the desired pattern and then contacting the coating withthe pattern face of the applicator.

5. The method of claim 2 wherein the etching medium is applied in latentform to an area of the metal coating broader than the desired patternand activated only in the desired pattern area.

6. The method of claim 1 combined with the step of metal coating thesubstrate.

7. The method of claim 6 wherein metal coating precedes etching mediumapplication.

8. The method of claim 6 wherein metal coating follows etching mediumapplication.

2. A continuous method of producing decorative or functionalbidirectional surface patterns on metal-coated substrate articlesutilizing adjacent areas of metallized and unmetallized surface on thesubstrate article by a print-etch process comprising contacting themetallic coating with a substantially nonspreading etching mixture inregions of the coating constituting the desired bidirectional patternand drying the mixture to form a chemical complex of the metal and theetchant mixture which contains essentially all the metal in the patternregion and which lacks at least one of the essential characteristics ofadhesion, reflectivity and conductivity of the metal coating per se,wherein the substrate is of web form and, wherein the inhomogeneous wetetching mixture comprises a solution of resin in an organic carrier andan aqueous etching solution, the organic carrier having a highervolatility than water so that upon drying the mixture, solidification ofthe resin is quickly obtained to prevent spreading of the etchant.
 3. Acontinuous method of producing decorative or functional bidirectionalsurface patterns on metal coated substrate articles utilizing adjacentareas of metallized and unmetallized surface on the substrate article bya print-etch process comprising contacting the metallic coating with asubstantially nonspreading etching mixture in regions of the coatingconstituting the desired bidirectional pattern and drying the mixture toform a chemical complex of the metal and the etchant mixture whichcontains essentially all the metal in the pattern region and which lacksat least one of the essential characteristics of adhesion, reflectivityand conductivity of the metal coating per se, wherein the etchantmixture comprises an etchant which is suitable for removing theparticular metallic coating, a body-forming component to preventspreading of the etchant mixture when applied to the particular coatedsubstrate surface involved and a volatile carrier therefor and acomponent which prevents the etching and body-forming chemicals fromshocking out when contacted with each other, and heating the contactedarea to remove the volatile component of the etchant mixture to form acomplex of the metal coating contacted with the mixture and the etchantcomponent only in the selected portion of the coating contacted by themixture.
 4. The method of claim 1 wherein the etching mixture is appliedto the metal coating by precoating a solid applicator having a patternface conforming to the desired pattern and then contacting the coatingwith the pattern face of the applicator.
 5. The method of claim 2wherein the etching medium is applied in latent form to an area of themetal coating broader than the desired pattern and activated only in thedesired pattern area.
 6. The method of claim 1 combined with the step ofmetal coating the substrate.
 7. The method of claim 6 wherein metalcoating precedes etching medium application.
 8. The method of claim 6wherein metal coating follows etching medium application.